Add virtual floor to shifted track design placement (OpenRCT2#22740)

distribution/changelog.txt

@@ -3,6 +3,7 @@
 - Feature: [#15642] Track design placement can now use contruction modifier keys (ctrl/shift).
 - Feature: [#21521] [Plugin] Add hook 'park.guest.softcap.calculate' called before calculating the soft guest cap.
 - Change: [#22596] Land ownership fixes described by .parkpatch files are now only considered on scenarios.
+- Change: [#22740] Add virtual floor to shifted track design placement.
 - Fix: [#2614] The colour tab of the ride window does not hide invisible cars (original bug).
 - Fix: [#15406] Tunnels on steep Side-Friction track are drawn too low.
 - Fix: [#21959] “Save this before...?” message does not appear when selecting “New Game”.

src/openrct2-ui/windows/TrackDesignPlace.cpp

@@ -21,6 +21,7 @@
 #include <openrct2/actions/TrackDesignAction.h>
 #include <openrct2/audio/audio.h>
 #include <openrct2/localisation/Formatter.h>
+#include <openrct2/paint/VirtualFloor.h>
 #include <openrct2/ride/RideConstruction.h>
 #include <openrct2/ride/RideData.h>
 #include <openrct2/ride/Track.h>
@@ -226,6 +227,8 @@ namespace OpenRCT2::Ui::Windows
                     });
                     res = GameActions::Execute(&tdAction);
                     cost = res.Error == GameActions::Status::Ok ? res.Cost : kMoney64Undefined;
+
+                    VirtualFloorSetHeight(trackLoc.z);
                 }
             }
 
@@ -440,6 +443,8 @@ namespace OpenRCT2::Ui::Windows
                     TrackDesignPreviewRemoveGhosts(*_trackDesign, *newRide, _placementGhostLoc);
                     _hasPlacementGhost = false;
                 }
+
+                VirtualFloorSetHeight(0);
             }
         }